The present invention generally pertains to injection molding of plastic products and is particularly directed to removal from a core mold part of a hollow injection molded product having a substantially tubular section that is formed in the mold cavity with two open ends.
One process of manufacturing a hollow plastic product with a substantially tubular section includes the steps of:
(a) providing a cavity mold part with a generally cylindrical portion for forming at least an outside segment of the substantially tubular section of the product;
(b) providing a core mold part with a generally cylindrical portion for forming at least an inside segment of the substantially tubular section of the product;
(c) combining the cavity mold part with the core mold part to configure a mold cavity for forming a product with a substantially tubular section;
(d) injecting plastic material into the mold cavity to form the molded plastic product; and
(e) separating the core mold part from the cavity mold part while retaining the molded product on the core mold part; and
(f) removing the molded product from the core mold part.
It is difficult to remove a molded product with a substantially tubular section from the core mold part because the injected plastic material shrinks upon cooling within the mold cavity and thereby causes the substantially tubular section of the molded product to adhere tightly to the generally cylindrical portion of the core mold part. Such difficulty is especially severe when the tubular section of the molded product is very thin and flexible.
It is known in the prior art to inject compressed air into an injection-molded hollow plastic product that is formed in the mold cavity with a substantially tubular section, one open end and one closed end in order to loosen the product from the core mold part.